This invention relates to methods and apparatus used to determine if adjacent concealed conductive elements, such as buried pipelines are physically separated from each other or in contact with each other.
Concealed conductive objects such as buried natural gas pipelines are frequently positioned adjacent to each other. If physical contact occurs between adjacent pipelines, associated cathodic protection systems used on those pipelines may be adversely affected and the rate of corrosion at the contact point may greatly increase. It is therefore desirable to determine if adjacent pipelines are in contact with each other without having to excavate the pipelines. Various techniques for locating underground pipelines and cables are well known. Typically, a test signal is inductively or conductively coupled to the pipeline and electromagnetic fields created by that signal are detected and processed to give an indication of the lateral location and depth of the pipeline. However, such techniques do not provide a reliable indication of physical contact or separation between adjacent pipelines. This invention seeks to provide such an indication.